E. I. du Pont de Nemours and Company (DuPont) has been making and selling Sontara.RTM. spunlaced fabrics for a number of years. Such spunlaced fabrics have a multitude of uses such as medical gowns and drapes, absorbent wipers and durables such as window shades and interlinings for apparel. Sontara.RTM. spunlaced fabrics are successfully marketed because of their low cost in use and valuable attributes such as texture, softness, comfort, drapability and absorbency.
Spunlaced fabrics are made by hydroentangling webs of fibers with high energy water jets as basically described in Evans et al. U.S. Pat. No. 3,485,706. The webs may be made of a variety of fibers such as polyester, rayon, cellulose (cotton and wood pulp), acrylic, and other fibers as well as some blends of fibers. The fabrics may be further modified to include antistatic and antimicrobial properties, etc. by incorporation of appropriate additive materials into the fiber or fiber webs. However, one limitation of spunlaced fabrics and nonwovens in general is durability through multiple launderings. Thus, spunlaced fabrics have not been acceptable for most uses in apparel and garments except for single use garments such as medical gowns and limited use protective apparel.
Hydroentangling creates an impressively strong fabric at much lower cost than weaving and knitting. Unfortunately, the cyclic working in a typical washer ravages the entangled fibers and effectively destroys the fabric for its intended purpose as fibers are disentangled. After a single laundering, the fabric may tend to have a noticeably poorer appearance such as a pilling or "worn" look or possibly may be destroyed. Within a few launderings, ordinary spunlaced fabrics are almost always useless for their intended purpose. The fabric has the appearance that it has been shredded.
In one approach to create durability in spunlaced fabrics, DuPont has addressed this problem by a stitch pattern introducing thread into the fabric forming a stitchbond structure. The filament or staple yarns are "knit" in a dense pattern into the fabrics and are quite resistant to the cyclic tensioning or working of the fabric. Thus, the laundered stitchbond fabric does not suffer as much of the damages seen with the ordinary un-reinforced spunlaced fabrics. The stitched structure has proven to be reasonably satisfactory in performance for durable and reusable mattress covers and withstands many hundreds of launderings. However, there are aesthetic and cost considerations of the stitched appearance that could make such a solution unattractive.
Others have attempted to create a durable nonwoven by adding bonding agents to the fabrics. The bonding agents tend to make the resulting fabrics quite stiff. Actually, it seems to take more bonding agent to make the fabrics durable than it does to make them stiff. Clearly, stiffness is not a desirable quality for a number of uses such as for apparel and home furnishings. A second problem with binders is that they often extend to the surface which creates a couple of undesirable consequences. The binders tend to be very hard after they are cured and any place that it extends through to the surface will be noticeable to the touch. It will feel like a pebble or similar structure which would be quite irritating. The second problem is that the binders often do not respond to dyes and printing like the fibers in the fabric. As such, the binder becomes noticeable and unsightly.
Clearly, it would be very desirable to be able to make and use nonwoven fabrics that are durable to withstand numerous launderings or similar abuse while having the qualities available from spunlaced fabrics.